Runnability of Web in a Material Web Machine

ABSTRACT

A runnability device, for example a runnability box such as a suction box, is for achieving improved runnability of a web when the web (W) progresses supported by a wire ( 61 ) to a closing gap between a roll and the wire. The runnability device ( 10 ) is located on the side of the wire before the roll and extends over the width of the web so that there is a slot between the wire and the runnability device. The runnability device comprises devices ( 11 ) for directing a vacuum from the side of the wire over the width of the closing gap so that the vacuum in the edge area (E) of the web wire is greater than in the central area of the web wire. A characteristic feature of the invention is that the vacuum device ( 11 ) which creates the vacuum effect is adjustable in the cross-direction of the web wire.

BACKGROUND OF THE INVENTION

The present invention is generally related to material web machines. More precisely, the present invention concerns a method and runnability device for achieving improved runnability of the material web in a material web machine, when the web progresses in the machine direction (MD), in other words in the direction of travel of the web, supported by a wire to a closing gap between the following support roll and the wire.

The present invention can be used for example in conjunction with a vacuum box in a drying unit of a material web machine, but the present invention can also be applied in conjunction with other types of drying unit concepts and web transfer concepts.

In the context of the present invention, the term material web machine refers generally to all types of machines used for the processing of web-like materials, where the web-like material can be:

-   a material web, which generally refers to all types of webs, or -   a fiber web, which generally and more specifically refers to various     types of paper webs, board webs, tissue webs, pulp webs etc., or -   a paper and/or board web.     For simplicity, in what follows the web-like material is referred to     as the web. In what follows, the fabric which supports the web is     referred to as the wire. In this way, the web and wire together form     the web wire. The material web machine can hence be specifically for     example a fiber web machine or for example a paper/board machine. In     the context of the present invention, the general term material web     machine is used.

FI publication 113973 presents a method and device for stabilizing the movement of a web wire in the press section of a material web machine in a rectilinear transfer of the web, while supported by a fabric, from one roll to a second roll, in other words on a support distance of the web wire. According to the publication, the web support device intensifies the vacuum effect on the fabric side in critical areas such as in the opening and closing gaps, and also in the edge areas of the web. In this case, suction slots which intensify the suction are connected to the critical areas by means of ejection nozzles. In the wide transverse central area of the web in machine and in cross-machine direction (CD), the vacuum effect is limited by arranging a controlled leakage flow or vacuum reduction flows implemented with limited counterblow. In this manner, according to the publication, a vacuum effect greater than before is concentrated to the adjacency of the support rolls of the fabric and to the edge areas of the web.

The operation of the presented felt suction box is influenced by sealing arranged completely with blowing, where the sealing also provides air to the transverse central area of the web, from where air then needs to be removed in addition to the flow of normal leakage air, in other words there is double effort when the same air is first blown and then sucked. The structure of felts is also considerably denser than that of drying wires, and felts carry significant amounts of water with them, so their contact with the suction box does not cause immediately as great friction forces as in drying wires, when impingement blowing also presses the wire towards the suction box and heats the web and wire. Forming sections and press sections generally include suction boxes which touch the wet wire or felt and which have a hardened and water-lubricated surface structure.

SUMMARY OF THE INVENTION

However, the specific problem with prior art continues to be that the edge of the web becomes loose from the wire at the gap which closes in the machine direction, at the edge areas of the gap which is formed between the wire and roll, when the web comes to the suction roll, such as to a vac roll or groove roll. In the context of the present invention, the edge area of the closing gap refers to that part of the closing gap which is in cross-machine direction (CD) at the edge of the gap, where the edge of the wire or web or web wire travels in the machine direction. The edge of the web becomes loose from the wire because of air brought by the roll and wire, and the goal is to remove this air:

-   by using a runnability box for removing air from the entire pocket     space bordered by the preceding roll as well as the closing gap     formed by the next roll and the wire, and -   by means of the interaction of blowing and removal suction exerted     directly on the web, for example by an optional blowing and suction     distance from the edge of the web.

In this case, great powers are needed so as to be able to eliminate the air accumulating in the closing gap in the edge areas from outside the web wire directly through the wire, by using a single vacuum level in the entire pocket. So that a vacuum could be created in the edge area of the closing gap, an unnecessarily high vacuum is created in the rest of the pocket space, in other words in the central area, with this high vacuum deflecting the wire towards the box. This type of deflection is harmful for example in impingement blowing, because the drying efficiency decreases as the distance grows, and when the drying efficiency is different in the center of the web wire than in the edges, a deviation in the cross-directional drying profile of the web takes place correspondingly at the edges. A small vacuum in the edge area also complicates tail threading and may cause for example folds in the web wire. Furthermore, a small vacuum in the edge area is harmful in view of edge trimming (width) of the web and control of impingement blowing. Another weakness in prior art technology is that it is difficult to adjust the location or width or intensity of the area of the vacuum effect in the edge area. These problems are highlighted and accentuated as the running speed of the web wire increases.

One of the goals of the present invention is to eliminate or at least essentially reduce the problems and weaknesses of prior art solutions.

Another goal of the present invention is to accomplish a new and inventive runnability device for achieving improved runnability of the web in a material web machine.

A third goal of the present invention is to ensure that the web remains in contact with the wire which supports the web.

A fourth goal of the invention is to reduce the deflection of the web wire and hence to even out deviations in the CD drying profile.

A fifth goal of the invention is to reduce runnability problems and hence to enable increased web running speeds.

A sixth specific goal of the present invention is to improve opportunities to adjust the location, width and/or intensity of the area of the vacuum effect in the edge area.

In general, the goals of the present invention can be accomplished by means of a runnability device according to the invention in order to achieve improved runnability of the web in a material web machine, when the web travels in the machine direction supported by a wire into a closing gap between a roll and the wire, where the runnability device is typically a runnability box, for example a suction box, which is located on the side of the wire before the said roll and extends essentially over the width of the web so that there is a slot between the wire and the runnability device, and where the runnability device comprises devices for directing a vacuum from the side of the wire over the width of the web wire and/or over the width of the closing gap in the cross-machine direction so that the vacuum in the edge area of the web wire and/or in the edge area of the closing gap is higher than in the central area of the web wire, for example so that the runnability device comprises a vacuum device which accomplishes a vacuum effect and which is adjustable in the cross-machine direction.

According to one example of the present invention, the vacuum device of the runnability device is adjustable in the cross-machine direction by means of seals or a seal package.

According to one application example of the present invention, the sealing device can be composed of a labyrinth seal package which comprises at least two labyrinth seals located at a distance from each other, where the essentially straight counter faces of the labyrinth seals border between them a suction slot, the cross-section of which is essentially a parallelepipedon. In this case, the vacuum effect is created by a direct suction to the edge area of the web wire and/or of the closing gap from the side of the wire through the labyrinth seal package, and by the boundary-layer flow of air traveling with the web wire into the sealing device, and by a potential vacuum inside the runnability box, with the suction slot being open to the inside of the runnability box. The advantages of a labyrinth seal package include for example that a sufficient vacuum effect is achieved while at the same time the seal package is simple and economical.

According to another application example of the present invention, the sealing device can be composed of an edge nozzle which employs the ejection principle, where the edge nozzle is made up of two wall sections located at a distance from each other and where the wall sections have shaped counter faces, which are directed towards each other and which border between them an air blow slot, which forms an edge nozzle operating according to the ejection principle. In this case, the vacuum effect is created by ejection blowing to the edge area of the web and/or of the closing gap in the ejection blow slot and by the air flow with the web wire over the blow slot and, when also using a suction slot, by a potential vacuum inside the runnability device, with the suction slot being open to the inside of the runnability device. The advantage of the nozzle device is that a great vacuum effect can be achieved even with a small air flow. The vacuum effect can be adjusted for example by adjusting the blow flow and/or separate suction flow.

According to the present invention, the sealing device can be adjusted in the cross-machine direction for example as follows:

-   by moving the sealing device on the wire side to an optional     distance from the edge of the web wire, whereby the location of the     vacuum effect in the edge area of the web wire and/or of the closing     gap can be adjusted, -   by adjusting the angle between the sealing device and the machine     direction, whereby the distance of at least one end of the sealing     device in the cross-machine direction or with respect to the web     wire in the vertical direction, in other words in the Z-direction,     from the edge of the web wire can change in the machine direction     depending on the distance to the closing gap so that especially the     intensity of the vacuum effect can be adjusted in the machine     direction in the edge area of the web wire, and/or -   by adjusting the width of the sealing device, in other words the     width of the suction slot at least on one end of the seal package or     edge nozzle, whereby the velocity of the air flow in the suction     slot can be influenced essentially so that the intensity of the     vacuum effect in the edge area of the web wire and/or of the closing     gap can be adjusted. -   The labyrinth sealing can also be carried out so that seals are     placed at an angle to the rectangular seal holder. In this case, a     holder placed in the machine direction can have a diagonal seal, and     the remaining labyrinth seals can be located on its both sides at a     distance. In this case, the labyrinth seal guides the boundary-layer     flow traveling with the wire away from the closing gap.

It is recommended that the sealing device, which can be adjusted in the cross-machine direction, be dimensioned and positioned so that it does not touch the web wire, which may deflect towards the runnability device by the effect of vacuum. However, some contact may occur between the web wire and the sealing device, and in order to avoid this contact or to minimize the resulting friction, the sealing device may be flexible in the direction of deflection of the web wire and/or potentially such that it wears at its contact locations to correspond to the shape of the deflecting wire. One preferred material for the sealing device is for example polytetrafluoroethylene such as sold under the trademark Teflon®.

As far as the other special features of the invention are concerned, reference is made to the accompanying specific description and the accompanying claims.

Of the advantages achieved with the present invention, it can especially be stated that the edge of the web remains in contact with the wire also during impingement blowing, that the shrinkage of the web is reduced, and that the deflection of the wire is reduced and the wire remains smoother. Further advantages include that the wire support rolls, which are for example vac rolls with vacuum throughout their surface, can be equipped with intensified vacuum forming in the edge area. In this case, the vac rolls can be provided for example with denser grooving or denser suction holes in its edge areas. Instead of or in addition to grooves or suction holes, the vac rolls can be provided with separate suction chambers in the edge areas so that a greater vacuum is formed.

In what follows, the invention is described by means of one embodiment arranged preferably in the drying unit of a paper machine by making reference to the accompanying patent drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents generally a runnability device according to the invention in the drying unit of a paper machine.

FIG. 2 presents a cross-section of an embodiment example of the runnability box according to the embodiment presented in FIG. 1, with the cross-section running along line A-A in FIG. 1.

FIG. 3 presents a cross-section of another embodiment example of the runnability box according to the embodiment presented in FIG. 1, with the cross-section running along line A-A in FIG. 1.

FIG. 4 presents two examples of the use of labyrinth seals and blow seals.

FIG. 5 presents a partial section view of the wire and web, seen from the top.

FIG. 6 presents a partial section view of the wire and web send from the side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The paper machine presented in FIG. 1 includes the forming section A, press section B, and dryer section C. In the press section B, the first cycle 1 and the second cycle 2 as well as the third cycle 3 are felt cycles, and the fourth cycle 4 in the press section is usually a transfer belt, but the cycle 4 can also be composed of a felt. The dryer section C includes the fifth cycle 5, which is a so-called transfer wire cycle, and the sixth cycle 6, which is typically a drying wire cycle. Naturally, other types of forming and press sections are suited in conjunction with the present invention.

In the example of FIG. 1, the first fabric cycle 1 and the second fabric cycle 2 in the press section B are partly against each other so that the fabric cycles support the web W continuously on at least one side. The third fabric cycle 3 and the fourth fabric cycle 4 in the press section are located on both sides of the web W, and they can be, as is illustrated in FIG. 1, also against each other partly so that the web travels supported by at least one of these fabrics. In the example of FIG. 1, the transfer wire cycle 5 in the dryer section C supports the web from above and the wire 61 of the drying wire cycle 6 supports the web from beneath.

In the dryer section C shown in FIG. 1, an impingement blowing hood 71 is arranged at the drying wire cycle 6, with the impingement blowing hood 71 arranged above the web W which travels supported by the wire 61 of the drying wire cycle. After the drying wire cycle, the web W travels to the next impingement blowing section 8, where the web W first travels downwards past the first impingement blowing hood 81 of the impingement blowing section and then upwards past the second impingement blowing hood 82 of the impingement blowing section.

Runnability device 10 is used for achieving improved runnability of the web, when the web travels in the dryer section C in the support distance 64 between the first roll 62 and the second roll 63 following the first roll, supported by the wire 61 of the drying wire cycle 6, into the closing gap 65 between the second roll 63 and the wire 61 in the machine direction. The runnability device is typically a runnability box, such as a suction box, which is located on the inner cycle of the wire 61 of the drying wire cycle 6 before the second roll 63 and extends essentially over the width of the web W so that there is a slot between the wire 61 of the drying wire cycle 6 and the runnability device 10. The runnability device comprises vacuum devices 11, 12, preferably suction devices or blow devices, for directing the vacuum from the side of the wire of the drying wire cycle in the cross-machine direction over the width of the web wire W, 61, which comprises the web W and the wire 61 of the drying wire cycle, and/or over the width of the closing gap 65.

Reference is made to FIG. 2, which presents a cross-section of an embodiment example of the runnability box according to the embodiment presented in FIG. 1, with the cross-section running along line A-A in FIG. 1. Due to the directed vacuum, the vacuum in the edge area E of the web wire and/or in the edge area 64 of the closing gap 65 is higher than in the central area of the web wire W, 61 and/or of the closing gap 65.

In order to direct the vacuum affecting the web W, which travels in the machine direction, through the wire 61 of the drying wire cycle 6, which supports the web, to the desired location in the edge area E of the web W and/or in order to adjust the intensity of the vacuum affecting the web W through the wire of the drying wire cycle, the runnability device 10 comprises a vacuum device 11, 12, which accomplishes a vacuum effect, with the vacuum device 11, 12 being adjustable in the cross-machine direction.

According to the embodiment example of FIG. 2, the vacuum devices 11, 12 in the runnability box 10 are limited by a seal package which can be adjusted in the cross-machine direction. According to the invention, such a seal package can be for example a labyrinth seal package 111, 112, which comprises at least two labyrinth seals arranged at a distance from each other. In this way, the labyrinth seals 111, 112 located at a distance from each other, with the counter faces of the seals being preferably straight, form a suction slot 13 a between them, and the sealing is open through the slot to the inner side of the runnability box. The vacuum slot 13 aconnects to a source of vacuum V1 and connects the source of vacuum to the edge areas of the wire 61. A source of vacuum V2 is connected to the central region of the wire 61.

Since the counter faces of the labyrinth seals 111, 112 are straight, the shape of the cross-sectional profile of the suction slot 13 a is a hyperbola, with one of the following counter faces in the direction of air flow:

-   parallel counter faces, in which case the air flow remains     essentially constant, -   convergent counter faces, with this shape causing damming up of the     air flow, or -   divergent counter faces, which intensifies the air flow in the     suction slot.     By adjusting the width and/or shape of the suction slot 13 a, the     intensity of the vacuum can hence be adjusted upstream of the     suction slot 13 a, in other words the intensity and location of the     vacuum affecting the web W through the wire 61 of the drying wire     cycle 6 can be adjusted.

When the vacuum device is a labyrinth seal package 111, 112, the vacuum effect in the edge area E of the web wire W, 61 and/or in the edge area 64 (see FIG. 1) of the closing gap 65 (see FIG. 1) is accomplished by a direct suction from the side of the wire 61 of the drying wire cycle 6 from between the labyrinth seal packages 111, 112. The air flow from between the labyrinth seal packages can also be influenced significantly by the boundary-layer flow of air traveling on the side of the wire of the drying wire cycle of the web wire W, 61 to the inner side of the labyrinth seal package and by a potential vacuum inside the runnability box 10, into which the sealing accomplished with the labyrinth seal package is open.

Reference is made to FIG. 3, which presents a cross-section of another embodiment example of the runnability box according to the embodiment presented in FIG. 1, with the cross-section running along line A-A in FIG. 1. According to this embodiment example, the sealing device in the runnability box 10 is composed of a nozzle device 12, which is an edge nozzle employing the ejection principle and which is arranged to operate together with the flow-restricting strip 14.

Such an edge nozzle 12 according to FIG. 3 is made up of two wall sections 121, 122 located at a distance from each other, where the wall sections 121, 122 have shaped counter faces, which are directed towards each other and which border between them a blow slot 13 b employing the ejection principle, with the blow slot 13 b comprising the following in order to accomplish an ejection effect in the direction of air flow:

-   first, a curved convergent gap part, then -   a reduction zone having a small flow cross-section, and finally -   an out-flow zone, which may also be expanding.     The vacuum effect through the wire 61 to the edge area E of the web     and/or to the edge area 64 of the closing gap 65 is hence arranged     by means of the blow slot 13 b(or suction slot 13 a). Moreover, air     flow with the web wire W, 61 on the side of the wire 61 of the     drying wire cycle 6 over the flow-restricting strip 14 to the     central area of the box can be removed by means of vacuum in the     runnability box 10.

When the vacuum device 12 in the runnability box is a blow slot employing the ejection principle, the vacuum is accomplished in the edge area E of the web wire W, 61 and/or in the edge area 64 of the closing gap 65:

-   by the blow slot 13 b employing the ejection principle, and -   by the air flow with the web wire over the blow slot, and -   by a potential vacuum from inside the runnability box, to where the     sealing of the vacuum devices is open.

Reference is made to FIG. 4, which presents two examples of the use of labyrinth seals 111, 112 and blow seals 12. The labyrinth seal can restrict the air flowing from the central area of the web wire to the edge areas more efficiently than the flow-restricting strip (14, cf. FIG. 3), in other words the deflection in the central area of the wire can be reduced, because the vacuum remains smaller. Correspondingly, a higher vacuum can be directed to the edge area. Especially during tail threading, a higher and more precisely directed vacuum is needed at the tail end. The left-hand side solution in FIG. 4, comprising a separate suction slot 13 a, produces a high vacuum also in locations where the blow sealing does not extend over the entire distance sealed. In this case, the blow sealing can be replaced for example with a mechanical seal, which closes the gap between the roll and wire from a cross-directional flow.

Reference is made to FIGS. 5 and 6, which present a partial section view of the wire and web, seen from the top and side, in other words the top view and side view. The arrows in FIGS. 5 and 6 illustrate the outgoing flow from the blow seals, with this flow following the coanda surface further down and turning away from the wire level as shown in the side view. Lateral seals describe the possibility to move them independently.

In the side view of FIG. 6, gap blowing is illustrated with arrows, which illustrate a more intense blow effect in the closing gap and a blow effect in the opening gap, which blow effect can be/is adjusted smaller. The opening gap can also be sealed mechanically.

In the top view of FIG. 5, the shadowing illustrates the various types of vacuums affecting the edge areas and central area of the web wire, with the control options of these vacuums being essentially improved by means of the present invention.

Within the basic idea of the invention, the sealing device can be adjusted in the cross-machine direction in many different ways. For example, the vacuum device 11, 12 can be moved on the side of the wire 61 of the drying wire cycle 6 to an optional distance from the edge of the web wire W, 61, whereby the location of the vacuum effect in the edge area E of the web wire and/or in the edge area 64 of the closing gap can be adjusted. Moreover, it is possible to adjust, simultaneously with the above adjustment or separately, the angle between the vacuum device and the machine direction, whereby the distance of at least one end of the sealing device in the cross-machine direction or in the Z-direction from the edge of the web wire can change in the machine direction depending on the distance to the closing gap 65. In this case, especially the intensity of the vacuum effect can be adjusted in the cross-machine direction in the edge area of the web wire. Moreover, the cross-directional angle of the sealing devices may prevent the formation of a boundary layer in the edge area of the closing gap. Furthermore, it is possible to adjust, simultaneously with the above adjustments or separately, the width of the suction slot 13 a of the sealing device, whereby the velocity of the air flow in the air slot can be influenced essentially so that especially the intensity of the vacuum effect in the edge area of the web wire and/or over the entire distance of the edge area of the closing gap can be adjusted.

According to the invention, it is recommended that the sealing device which can be adjusted in the cross-machine direction does not touch the web wire W, 61 so that friction resulting from the contact can be minimized between the moving wire 61 of the drying wire cycle 6 and the stationary sealing device 111 , 112, 14. However, it may be advantageous that the sealing device is flexible in the direction of deflection of the web wire and/or potentially such that it wears at its contact locations to correspond to the shape of the wire of the drying wire cycle, with this wire deflecting to the web wire. In this case, one recommended sealing device material is Teflon®.

The invention is described above only using an example of a preferred embodiment. However, the invention is in no way confined to only concern such an individual embodiment example, but within the scope of protection of the inventive idea specified by the accompanying claims, many alternative solutions and modifications as well as functionally different alternatives are possible.

It is therefore to be noted that the location of the runnability box is naturally not confined to the drying unit alone, but the present invention can be applied in any processing unit of a paper machine, or more generally, of a material web machine, where there is a need to ensure that the web remains in contact with the wire. It is also to be noted that instead of placing the runnability box in a single support distance in a processing unit or units of a material web machine, the runnability box can also be placed in several support distances (see for example FIG. 1). In general, it is advantageous but not necessary that the preferred application location of the present invention is in conjunction with impingement blowing, which is why the present invention can also be as such a solution to the problem of how to keep the web in contact with the wire. 

1. A runnability device in a material web machine comprising: a roll in the web machine; a wire arranged to travel in a machine direction over the roll to form a closing gap with the roll, the closing gap having edge areas with a central area therebetween, the wire having a first side which engages the roll; a web arranged to travel in a machine direction over the roll with the wire to define with the wire a web wire, wherein the web wire has edge areas with a central area therebetween and; a runnability device located on the first side of the wire, and positioned before the said roll and which extends essentially over the width of the wire so that there is a slot between the wire and the runnability device; wherein the runnability device further comprises vacuum devices for directing a vacuum from the first side of the wire over the width of the web wire or over the width of the closing gap in the cross-machine direction such that the edge areas of the web wire or the edge areas of the closing gap are connected to a first source of vacuum which has a greater vacuum than a second source of vacuum, which second source of vacuum is connected to the central area of the web wire or the central area of the closing gap; and wherein at least one adjustable device which is arranged to connect the first source of vacuum to one edge area is mounted to be adjustable in a cross-machine direction.
 2. The runnability device of claim 1 wherein the at least one adjustable device comprises vacuum seals.
 3. The runnability device of claim 2 wherein the vacuum seals comprise at least two labyrinth seals located at a distance from each other.
 4. The runnability device of claim 3 wherein the labyrinth seals have essentially straight counter faces and form between them an air slot connected to the first source of vacuum.
 5. The runnability device of claim 3 wherein the second source of vacuum is at least one of the labyrinth seals.
 6. The runnability device of claim 2 wherein the first source of vacuum is a nozzle device which employs the ejection principle.
 7. The runnability device of claim 6 wherein the nozzle device is a blow nozzle, having two wall sections located at a distance from each other, and wherein the wall sections have shaped counter faces, which are directed towards each other and which define between them a blow slot.
 8. The runnability device of claim 7, wherein the second source of vacuum is formed by at least one wall section of the blow nozzle.
 9. The runnability device of claim 1 wherein the at least one adjustable device mounted to be adjustable in a cross-machine direction is adjustable in a Z-direction with respect to the wire so that a vacuum effect intensity can be adjusted in the machine direction.
 10. The runnability device of claim 1, wherein the at least one adjustable device mounted to be adjustable in a cross-machine direction comprises: an adjustable width suction slot so that velocity of the air flow in the suction slot can be influenced to adjust vacuum intensity at the edge areas of the web wire and/or in the edge areas of the closing gap.
 11. The runnability device of claim 1 wherein the wire does not touch the at least one adjustable device.
 12. The runnability device of claim 1 wherein the at least one adjustable device is arranged to wear to correspond to a shape taken by the wire.
 13. The runnability device of claim 11, wherein the at least one adjustable device is constructed of polytetrafluoroethylene.
 14. A runnability device in a dryer section of a paper machine, having an impingement blowing hood positioned above a plurality of vacuum rolls and a wire extending in a machine direction between said plurality of vacuum rolls, and the wire positioned between the impingement blowing hood and the vacuum rolls, the wire having a first side which engages the rolls and the wire having a first edge area and a second edge area with a central area therebetween, the runnability device comprising: a vacuum box positioned between two of said plurality of vacuum rolls, the vacuum box spaced from the wire first side to define a slot, and extending in a cross machine direction with respect to the wire; at least one first source of vacuum; a second source of vacuum which has less vacuum than the at least one first source of vacuum; a first sealing device mounted for cross machine direction motion, and arranged to separate a first edge portion of the vacuum box from a central portion of the vacuum box; a second sealing device mounted for cross machine direction motion, and arranged to separate a second edge portion of the vacuum box from the central portion of the vacuum box, the central portion of the vacuum box being between the first edge portion of the vacuum box and the second edge portion of the vacuum box; wherein the first edge portion of the vacuum box is connected to the at least one first source of vacuum to draw a vacuum on the first edge area of the wire; wherein the central portion of the vacuum box is connected to the second source of vacuum to draw a vacuum on the center area of the wire; and wherein the second edge portion of the vacuum box is connected to the at least one first source of vacuum to draw a vacuum on the second edge area of the wire, or is connected to a second first source of vacuum to draw a vacuum on the second edge area of the wire.
 15. The runnability device of claim 14 further comprising: a first nozzle device which is arranged to employ the ejection principle, and which forms the at least one first source of vacuum; and a second nozzle device which is arranged to employ the ejection principle and which forms the second first source of vacuum.
 16. The runnability device of claim 15 wherein the first nozzle device is made up of two wall sections located at a distance from each other, wherein the wall sections have shaped counter faces, which are directed towards each other and wherein a border is located between them which defines a blow slot having a curved convergent gap part, followed by a reduction zone having a small flow cross-section, and followed by an out-flow zone; and wherein the second nozzle device is made up of two wall sections located at a distance from each other, wherein the wall sections have shaped counter faces, which are directed towards each other and wherein a border is located between them which defines a blow slot having a curved convergent gap part, followed by a reduction zone having a small flow cross-section, and followed by an out-flow zone
 17. The runnability device of claim 14 wherein the first sealing device and the second sealing device are labyrinth seals.
 18. The runnability device of claim 14 wherein the first sealing device comprises a pair of spaced apart labyrinth seals, said pair of labyrinth seals defining the first edge portion of the vacuum box; and wherein the second sealing device comprises a pair of spaced apart labyrinth seals, said pair of labyrinth seals forming the second edge portion of the vacuum box. 